Various exhaust after-treatment devices, such as diesel particulate filters, three-way catalysts, and other devices, have been developed to effectively limit exhaust emissions from internal combustion engines. In the case of compression-ignition or diesel engines, a great deal of effort continues to be expended to develop practical and efficient devices and methods for reducing emissions of largely carbonaceous particulates in exhaust gases.
An oxidation catalyst is one of the devices that are often provided in diesel engines for such a purpose. Such an oxidation catalyst is typically employed in order to oxidize and burn hydrocarbon emissions present in the exhaust flow. However, when a diesel engine is operated at idle for an extended period of time, hydrocarbon emissions may become deposited on the oxidation catalyst. A significant accumulation of hydrocarbon emissions on the oxidation catalyst may cause elevated temperatures and eventual damage to the catalyst. A similar concern may develop in three-way catalysts that are commonly used in spark-ignition or gasoline engines.